Battery Isolator solution?

I think I figured out how I am going to set up the electric of my car...

Use a battery isolator and connect a second battery (deep cycle) in the trunk, that will power the inverter, which in turn will power the PC. I'll build a carpeted box w/ exhaust fans and have the PC, inverter, fuse block, and battery inside.

This way it gives me an excellent power solution with a pretty easy hookup. However, Ive seen battery isolators range from $30 to $129 for almost the same rating! I've been told hellroaring.com makes some of the best units, but is there something a little cheaper that works as good? I've found a few on marine web sites... but they are generic brand. Any feed back is welcome! thanks!

I use a battery isolator in my setup, however mine is very expensive. I use a Xantrex Pathmaker. Since I sometimes have a camper on my truck i needed to be able the isolate 3 separate battery banks. Anyway, this is a solenoid relay type isolator which produces no voltage drop. A cheaper diode based isolator is gonna drop the voltage down .7 volts, which may or may not be a factor for you. I know that the hellroaring is a good unit. Search for soleniod isolators maybe you can find a simple cheap one. Just be sure to get one that can handles the amount of amps that your alternator can produce. I personally think that if you can squeeze an extra deepcell battery in your car its by far the best tank solution. I survive my cranks and can run my carputer with the car off for hours on end with no probs.

I think I figured out how I am going to set up the electric of my car...

Use a battery isolator and connect a second battery (deep cycle) in the trunk, that will power the inverter, which in turn will power the PC. I'll build a carpeted box w/ exhaust fans and have the PC, inverter, fuse block, and battery inside.

This way it gives me an excellent power solution with a pretty easy hookup. However, Ive seen battery isolators range from $30 to $129 for almost the same rating! I've been told hellroaring.com makes some of the best units, but is there something a little cheaper that works as good? I've found a few on marine web sites... but they are generic brand. Any feed back is welcome! thanks!

i built a sproggy and cutdown the power load off the battery by half. that gave me enough power to run my other accessories in the car. my ac-dc inverter which i have used for years have finally came to rest together with all the headaches of noise, beep warning, surprise rebooting, etc. as i have experienced it, dc-dc is the best power solution.

my sproggy(mastero mk3.5) can survive 3 sec. crank and can run my carputer for 1 hour with engine off but i just want to take some load off my main batt. so i'm getting my deep cycle batt. next week as my "tank". for batt. isolator, i'll just use Ricky327's "relay based" tank circuit plus a bit of modification by myself. it is i to my conclusion, much better that using diodes(continues supply to backup batt. & decreased voltage). relay based tank circuit only deliver extra current to backup batt(tank) if there is 12v on the relay.

you're right, commercial products are so expensive. if you have some spare time, and a natural diy'er, the cheapest way is to built it yourself. help is just right at the corner.

use a diode, and a couple of relays and walla, you got your self a isolator.
I also put a 1n4001 diode on the positive wire going from the car battery to my backup. make the the stripe on the diode is facing the back up battery. This will keep the car from drawing power from your backup battery. I use this relay setup below also with my inverter and the $6 backup nicd I bought from a guy on this board.
this is what I did, compliments to "the specialist" for all the help, works works awsome..
"Since you only want the battery to charge when the PC is on, since we have no way of shutting off the charging cycle, you need the PC on to draw some juice away from the abttery do it doesn't overcharge.

Yo accomplish this, you basically wire a relay and hook it up to a molex so it connects the backup battery only when the PC is powered on and the 12 volt line on the molex is throwing out 12 volts.

Now this solves issues such as the accesory cuttingout during crank, the molex 12 wont cutoff during crank leaving teh relay connecting hte backup battery and wa la. No reboot. Well if I planned it right, I hope.

Does that make sense? I'm suprised no one ran the relay turn-on from the PC PS 12 volt Molex. I love my great ideas.